Railway track circuit apparatus



Nmf.12,194o. WRPLACE 2,221,653

RAILWAY TRA-CK CIRCUIT APPARATUS i originl Filed Aug. 3, 1938 l v WSW "X' la @@@-@Q-l g t a. g l l Hg?.

. Y v I wald INVE'N/BLI I .Bx

Patented Nov. 12, 1940 UNITED STATES PATENT CFFICE RAILWAY TRACK CIRCUIT APPARATUS Original application August 3, 1938, Serial No. 222,883, now Patent No. 2,197,414, dated April 6 Claims.

My invention relates to railway track circuit apparatus, and particularly to apparatus for track circuits using coded direct current.

The present application is a division of my co- I pending application Serial No. 222,883, filed August 3, 1938, now U. S. Patent No. 2,197,414, granted April 16, 1940 for Signal systems.

In railway signal systems of the type herein contemplated track circuits using coded direct 10I current are proposed. Recurrent or code impulses of direct current of positive polarity are employed to reect one traiiic condition, recurrent impulses of direct current of negative polarity are employed to reflect a second traiiic condition,

and recurrent impulses of direct current alternatcly positive and negative in polarity are used to reflect a third traino condition. The code rate, that is, the rate at which such current irnpulses are made to occur is preselected as desired and may be for example of the order of 120 impulses per minute in which case the code cycle interval is of the order of one-half second. Each individual impulse is short in duration as compared with the code cycle interval. In other words the individual impulses of current are short in duration as compared with the interval between successive impulses.` Slow acting relays are selectively governed in accordance with the polarity code of such current impulses, the slow acting periods of such relays being preferably just sufcient to span the duration between successive impulses of the same code. In transferring from one code to another it is essential that the interval between the last impulse of the old code and the rst impulse of the new code be not greatly diiferent from the interval between successive impulses of the same code in order that improper operation of the slow acting relays may be avoided.

Accordingly, a feature of my present invention is the provision of novel and improved track circuit apparatus wherewith the transfer from the supply of code impulses of direct current of positive polarity to the supply of code impulses of directA current of negative polarity or vice versa is effected in a specified sequence and an unduly long interval between the last impulse of the old code and the first impulse of the new code is 50 avoided and improper release of slow release signal controlling relays governed by such impulses of current is prevented. Other features and advantages of my invention will appear as the specication progresses.

55. In the accompanying drawing, Fig. 1 is a dia.-

Divided and this application September 26, 1939, Serial No. 296,600

(ci. 24e- 34) grammatic view showing a preferred form of apparatus embodying my invention, and Figs. 2 and 3 are diagrams illustrating operating characteristics of the apparatus of Fig. 1.

Referring to Fig. 1, the'track rails la and lb 5 I of a stretch of railway track over which traffic normally moves in the direction indicated by .an arrow are formed by insulated rail joints into' consecutive track sections of which only one section W-X and the adjoining ends of the two ad- 10; jacent sections are shown for the sake of simplicity. Each track section is provided with a track circuit comprising the track rails, a source of recurrent or code impulses of direct current connected across the rails at one end of thev secl5; tion, and a code responsive relay means connected across the rails at the other end of the section. Thus the source of current impulses for the track circuit of section W--X and the code responsive relay means of the track circuit for the 20 track section next in advance of section W--X, are located adjacent the junction W of the two track sections. The means for supplying the code impulses of direct current to the track circuit of a section is governed by the code responsive relay 25 means of the track circuit for the section next in advance in accordance with traiic conditions in advance. Thus the supply of code impulses of current to the track circuit of section W--X is governed by the code responsive relay means for 30 the track circuit for the section next to the left of section W--X as viewed in Fig. 1.

As illustrated in Fig. 2, clear traffic conditions in advance of a section are reflected by current 35 impulses alternately of positive and negative polarity being supplied to the track circuit of the section, approach restricting trafiic conditions in advance are reected by current impulses of positive polarity being supplied to the track circuit, and approach traflic conditions in advance are reflected by current impulses of negative polarity being supplied to the track circuit. A stop or slow speed traffic condition is reflected by the absence of any such current impulses. It is to be observed from Fig. 2 that, preferably there are twice as many impulses of current per minute transmitted under clear traffic conditions as transmitted under either approach restricting or approach trafc conditions.

The means for supplying code impulses of direct current to the track circuit for section W-X includes a track battery 2, a code transmitter CTI, a. track transformer or reactor TI, and two relays R3 and R4. The lower portion of ywinding 55 4 of track transformer TI is connected across the rails of section W-X at the exit end of the section, while the full winding 4 of transformer TI is connected with track battery 2 over contacts of code transmitter CT! and contacts of relays R3 and R4, relays R3 and R4-being controlled by traic conditions in advance and acting to pole change the connection of battery 2 with winding 4. A condenser 82 may be connected across winding 4. The code transmitter CTI may be of any convenient type, a preferred form being that covered by United States Letters Patent No. 1,913,826, granted June 13, 1933 to H. G. Blosser for Oscillating motors, when such oscillating motor is' improved in a manner to shortly appear so as to transfer from supplying current impulses of positive polarity to supplying current impulses of negative polarity or vice versa in a specified sequence. It is sufficient at this point of the specication to observe that as long as a current source whose terminals are B and C con.-

tinues .to supply current to Winding 8U of thek code transmitter CTI, an armature 8I is oscillated at a predetermined rate to alternately operate right-hand coding contacts 'II and 'I2 and left-hand coding contacts I5 and 16 as Well as to operate certain cam operated contacts 66, 68 and 'I9 once each operating cycle. The rate at which code transmitter CTI operates is preselected and for the purpose of illustration it may be assumed that the code transmitter is operated at the code rate of 120 operations per minute. The manner whereby code transmitter CTI and relays R3 and R4 govern the connection of battery 2 to transformer TI for supplying recurrent impulses of current to the track circuit of section W--X will be taken up and described when the operation of the apparatus is explained.

In the present embodiment of my invention the code responsive relay means for each track circuit includes two code following relays one responsive only to current of positive polarity and the other responsive only to current of negative polarity. Looking at the right-hand end of Fig. 1 the code following relays for the track circuit of section W-X are relays XTRI and XTRZ whose operating windings' are connected in parallel across the track rails of the section through asymmetric units, one unit being interposed in series with the winding of relay XTRI and another unit being interposed in series with the winding of relay XTRZ. These asymmetric units are so disposed that only current of what I shall call positive polarity is passed from the track rails to relay XTRI to energize that relay and only current of negative polarity is passed from the track rails to relay XTRZ to energize that relay. In a similar manner two code following relays W'IRI and WTR2 are included in the track circuit for the section next in advance of section W-X. The code following relays of a track circuit are used to govern repeater relays which repeater relays are the same for all track circuits. Looking at the left-hand portion of Fig. 1 the code following relays WTRI and WTR2 govern three slow release repeater relays WSI, WS2 and WS3.

Assuming at the start that the relays WSI, WS2 and WS3 are all deenergized and clear traffic conditions exist for the section next in advance of section W-X so that the current impulses supplied to the track circuit for the section next in advance are alternately positive and negative in polarity and the first impulse is one of positive polarity, the relay WTRI is operated and the relay WSI is energized over a simple circuit including a front contact of relay WTRI. The next impulse is of negative polarity and relay WTR2 is operated and relay WS2 is energized over a front contact of relay WTR2, vrelay- WSI remaining picked up by virtue of its'slowreleaseiperiod. A condenser 55 is charged over a circuit including battery terminal B, back contact 56 of relay WS3, back contact 51 of relay WTRI, front contacts 58 and 59 of relays WS2 and WSI, respectively, condenser 55 and terminal C. The next impulse of track circuit current is of positive polarity and relay WTRI is picked up to again energize relay WSI, relay WS2 remaining picked up due to its slow release period. The condenser 55 now discharges through a Winding of relay WS3 and relay WS3 is picked up, the circuit extending from condenser 55 over front contacts 59 and 58 of relays WS2 and WSI, respectively, front contact 60 of relay WTRI, top winding of relay WS3 and to condenser 55. From this point on relay WS3 is maintained energized over a stick circuit including its lower winding and front contact 6I, and front contacts 62 and 63 of relays WSI and WS2, respectively. It follows that relay WS3 is picked up only in response to three impulses of track circuit current of alternate polarity, but when picked up it remains picked up as long as the track circuit impulses are alternately positive and negative` in polarity.

In the event approach restricting traiflc conditions exist for the section next in advance of section W-X and code impulses of current of positive polarity are supplied to its .track circuit, relay WTRI is operated but relay WTR2 is inactive and hence relay WSI is energized and picked up but relays WS2 and WS3 are both released. Again, if approach traffic conditions exist for the section next in advance and code impulses of current of negative polarity are supplied to its track circuit, relay WTR2 is operated but relay WTRI is inactive and repeater relay WS2 is picked up but relays WSI and WS3 are released. Again, if the section next in advance is occupied and the track circuit is shunted so that both code following relays WIRI and WTR2 are inactive then all three repeater relays WSI, WS2 and-WS3 are released.

The code following relays XTRI and XTRZ associated with the track circuit for section W-X, as well as the code following relays of all other track circuits of the system, govern repeater relays in the same manner that code following relays WTRI and WTR2 govern the repeater relays WSI, WS2 and WS3; and the repeater relays associated with code following relays XTRI and XTRZ are not shown in order to not unduly complicate the drawing.

As shown in the lower left-hand portion of Fig. 1 the operating circuits for a four indication color light wayside signal WS for the section next in advance are governed by the repeater relays WSI, WS2 and WS3. These operating circuits will be readily understood by an inspection of Fig. 1 and need not be described in detail since they formv no part of my invention, and would be in accordance with standard practice.

The repeater relays WSI and WS2 also govern relays R3 and R4 which latter relays are in. cluded in the means for supplying current i1n` pulses to the track circuit for section W-X stated hereinbefore. Relay R3 is controlled over a simple circuit including front contact 64 of relay WSI. Relay R4 is controlled by a pick-up circuit including front contact S5 of rela'y WS2 and cam operated contact 66 of code transmitter CTI, the circuit extending from terminal B over winding of relay R4, front contact 55 of relay WS2, cam operated contact 66 of code transmitter CTI when closed and to terminal C. Relay R4 is also controlled over a rst stick circuit including its own front contact 61 and two cam operated contacts 68 and 19 of code transmitter CTI in `multiple in a manner as will be shortly described. Relay R4 is also controlled by a second stick circuit including front contact 65 of relay WS2 and its own front contact 83.

In describing the operation of the apparatus I shall assume rst that the section next in` advance of section W-X is occupied so that both repeater relays WSI and WS2 are released causing both relays R3 and R4 lto be deenergized and released. Under this condition the track battery 2 is connected across the winding 4 .of transformer TI over back contacts 69 and 10 of relay R4 and the right-hand coding contacts 1I and 12 of the code transmitter CTI, and energy is stored in the magnetic circuit of transformer TI, the time constant of the circuit being such that energy builds up slowly and no effective electromotive force is induced in the winding 4 and in turn applied to the rails of section W-X. When code transmitter CTI causes contacts 1I and 12 to be opened the magnetic energy stored in transformer TI decays rapidly and an effective electromotive force is induced in winding 4 and in turn is applied to the rails of section W--X causing an effective current impulse to flow in the track circuit of the section. The connections are such that the effective current impulse supplied through transformer TI to the track circuit for section W-X at this time is of negative polarity. Hence current impulses of negative polarity of the code rate corresponding to the rate at which code transmitter CTI is operated are supplied to the track circuit to reflect approach tralic conditions. l

When approach traffic conditions exist in ad- Vance so that the track circuit of the lsection next in advance is supplied with current impulses of negative polarity and relay WS2 is picked up closing front contact 65, the relay R4 is picked up in a manner to shortly appear. Battery 2 is now connected across winding 4 over front'contacts 13 and 14 of relay R4 and the left-hand coding contacts 15 and 16 of the code transmitter. The connection of battery 2 being opposite to that previously described, the track circuit for section W-X is now supplied with code impulses of current of positive polarity to reilect approach restricting trafc conditions for section W-X.

When approach restricting traffic conditions exist in advance and relay WSI is picked up, the

relay R3 is energized and relay R4 is released.

Battery 2 is now connected across winding 4 over back contacts 69 and 10 of relay R4 and the righthand coding contacts 1I and 12 to Supply the track circuit of section W-X withl impulses 5 of negative polarity, and battery 2 is also con- 75 when clear traffic conditionsvexist inv advance and both relays WSI and WS2 are picked up to energize both relays R3 and R4, the battery 2 is reversibly connected across Winding 4 as willy be evident from Fig. 1 so that impulses of current alternately of positive and negative polarity are supplied to the track circuit of section W-X to reiiect clear trafc conditions.

In changing from approach restricting to approach traffic conditions or vice versa it is preff erable to do so in a selected sequence so that the first impulse of reversed polarity appears in onehalf of the usual cycle interval. If the time is extended to one and one-half cycle intervals a false signal ash may result because of an improper release of a slow release repeater relay Whose slow release period is of the order of one cycle interval of the code transmitter. Hence i relay R4 which controls the supply of current to the track circuit should be picked up and released only at selected points in the cycle of code transmitter CTI, such points being selected to avoid an extended interval between impulses at a change of traflic conditions. For example, if traffic conditions change from approach to approach restricting and relay-R4 is energized and picked up at the instant the code transmitter CTI happens to be changing from the right-hand contacts 1I and 12 to the left-hand contacts 15 and 16 no eiective current impulse ywould be transmitted to the track circuit of section W-X the first time left-hand contacts 15 and 16 are operated, and there would be an interval of substantially one and one-half cycles before an impulse of positive polarity appears in the track circuit of section W-X and which long interval might cause improper release of an associated repeater relay. Again when trafc conditions change from approach restricting to approach it is undesirable to release relay R4 when the code transmitter is changing from left-hand contacts 15 and16 to the right-hand contacts 1I and 12 because no effective impulse would be supplied the rst time contacts 1I and 'I2 are operated and an interval of substantially one and one-half cycles would occur between the last impulse of the old code and the rst impulse of the new code. Such long delay between impulses is illustrated by the lower diagram of Fig. 3. To effect a proper sequence in changing from approach restricting to approach trafc conditions or vice versa, as illustrated by the top diagram of Fig. 3, the code transmitter CTI is provided with cam operated contacts 66, 68 and 19, which function to allow relay R4 to pick up or release as the case maybe only during a particular part of the operating cycle of the code transmitter. Relay R4 is picked up as explained hereinbefore over a pick-up cir'- cuit extending from terminal B through winding ofrelay R4, front contact of relay WS2, cam operated contact'BS, and to terminal C, and cam operated contact 66 is closed only during that part of the cycle of the code transmitter .CTI during which. the right-hand contacts 1I and 12 are closed. Hence relay R4 can be energized only when the right-hand contacts 'II and 12 are closed so that when on the next half cyclef of the transmitter CTI the left-hand contacts 15 and 16 are operated an effective impulse of current of positive polarity is supplied t0 the track circuit of section W-X. 4 b

Relay R4 is retained energized over its rst stick circuit including terminal B, winding of relay R4, front contact 61 and cam operated contacts 68 and 19 in parallel, and terminal C, as well as over its second stick circuit including terminal 'B;'Wind ing of relay R4, front contact 65 of relay WS2, front contact 83 of relay R4 and terminal C. Hence, if relay WSZ is released in response to a change in traffic conditions to open the second stick circuit, relay R4 is not released until such time as both contacts 68 and 'i9 are open to open the first stick circuit. Contact 19 is directional and opens only on the swing of the code transmitter to the right of each operating cycle, that is, during the instant the transfer is being made away from the left-hand contacts 'l5 and 16. Contact 68 is open during the cycle interval the left-hand contacts 15 and 'i5 are open. It follows therefore that relay R4 is released closing back contacts 69 and it just as the code transmitter operates to open the left-hand contacts 'l5 and 76 with the result that the next time the right-hand contacts ll and 'l2 of code transmitter l CTI are operated an impulse of current of negative polarity is supplied to the track circuit of section W-X. It is to be seen, therefore, that with the code transmitter CT! constructed in the manner just described it is possible to pick up and release relay R4 to transfer from approach restricting to approach traffic conditions or vice versa only at preselected points in the operating cycle of the code transmitter with the result that only a one-half cycle interval occurs between the last impulse of the old code and the first impulse of the new code and an improper release of an associated signal controlling repeater relay and a resultant signal flash are prevented.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track formed with an insulated track section, a source of direct current, a code transmitter having a preselected cycle interval and provided with a first and a second coding contact which contacts are alternately operated each operating cycle substantially one-half cycle interval apart, said transmitter provided with a rst and a second cam operated contact which contacts are operated at preselected points of each operating cycle, a trailic controlled relay, a rst circuit means including a front contact of said relay and said first coding contact to connect said current source withithe rails of said section for supplying to the rails code impulses of current of positive polarity with successive impulses spaced apart said operating cycle interval, a second circuit means including a back contact of said relay and said second coding contact to connect said current source with the rails of said section for supplying to the rails code impulses of current of negative polarity with successive impulses spaced apart said operating cycle interval, and a control circuit means including a traic controlled contact opened or closed according to a first or a second trafiic condition in advance of said section and having said cam operated contacts interposed therein to cause said relay to be picked up and released at predetermined points of said operating cycle to transfer from current impulses of positive polarity to current impulses of negative polarity or vice versa in substantially one-half of said operating cycle interval.

2. In combination, a stretch of railway track formed with an insulated track section, a source of direct current, a code transmitter having a preselected cycle interval and provided with a iirst and a second coding contact which contacts are alternately operated each operating cycle substantially o-ne-half cycle interval apart, said transmitter provided with a first and a second cam operated contact which contacts are operated at preselected points of each operating cycle, a transformer having a Winding connected across the rails of said section., a trailic controlled relay, a first circuit means including a front contact of said relay and said first coding contact to connect said current source with a winding of said transformer for supplying to the rails code impulses of current of positive polarity, a second circuit means including a back contact of said relay and said second coding contact to connect said current source with a winding of said transformer for supplying to the rails code impulses of current of negative polarity, and a control circuit means including said first and second cam operated contacts and a traiiic controlled contact open or closed according to a rst or a second traiiic condition in advance of said section to control the picking up and releasing of said re lay for governing the transfer from current impulses of positive polarity to current impulses of negative polarity or vice versa when there is a change in traffic conditions in advance.

3. In combination, a stretch of railway track formed with an insulated track section, a source of direct current, a code transmitter having a preselected cycle interval and provided with a rst and a second coding contact which contacts are alternately operated each operating cycle substantially one-half cycle interval apart, said transmitter provided with a rst and a second cam operated contact means which contact means are operated at preselected points of each operating cycle, a transformer having a winding connected across the rails of said section, a relay normally energized over a stick circuit including a trafc controlled contact which is closed in response to a first traffic condition in advance of the section and is open in response to a second traiiic conditio-n in advance, means including a front contact of said relay and said first coding contact to connect said current source with a winding of said transformer for supplying to the rails code impulses of current of positive polarity, other means including a back contact of said relay and said second coding contact to connect said current source with the last mentioned winding of the transformer for supplying to the rails code impulses of current of negative polarity, a pick-up circuit including said traffic controlled contact and said first cam operated contact means and arranged to pick up said relay only when said second coding contact is closed, and another stick circuit including said second cam operated contact means for said relay and arranged to permit the release of the relay only when said first coding contact is closed whereby said relay is picked up and released at preselected points of the operating Cycle to cause the transfer from positive to negative current impulses or vice versa to take place in substantially one-half cycle interval when traii'ic conditions change.

4. In combination, a stretch of railway track formed with an insulated track section; trackway coding means including a source of direct current, a code transmitter and a transformer the latter of which has a winding connected with the rails of said section; said code transmitter having a preselected operating cycle and provided with a right-hand and a left-hand contact each of which is closed and opened each operating cycle; said transmitter also provided with a first, a second and a third cam operated contact with said rst contact closed only when said right-hand contact is closed, said third contact closed only when said left-hand Contact is closed and said second contact opened only as said transmitter operates in the direction to close said right-hand contact; a relay, circuit means including a front contact of said relay in series with said left-hand contact of said transmitter or a back contact of said relay in series with said right-hand contact of said transmitter to connect said current source r with a winding of said transformer for supplying to the rails code impulses of direct current of either positive or negative polarity accordingA as said relay is picked up or released, a pick-up circuit for said relay including said first cam operated contact of said transmitter, 'a stick circuit for said relay including in multiple said second and said third cam operated contacts of said transmitter, and another stick circuit for said relay including a contact controlled by traiiic conditions in advance of said section.

5. In combination, a stretch of railway track formed with an insulated track section, a track transformer having a winding connected across the rails of said section, a source of direct current, a code transmitter having a preselected operating cycle for alternately operating a pair of right-hand and a pair of left-hand contacts; said code transmitter provided with a rst, a second and a third cam operated contact each of which is operated at a preselected point of the operating cycle; a traiic controlled relay, a first supply circuit including a pair of front contacts of said relay and said pair of left-hand contacts of said transmitter to connect said current source across a winding of said transformer and poled for supplying to the rails a current impulse of positive polarity each said operating cycle, a second supply circuit including a pair of back contacts of said relay and said pair of right-hand contacts of said transmitter to connect said current source across a winding of said transformer and poled for supplying to the rails a current impulse of negative polarity each said operating cycle, a pick-up circuit including a traffic controlled contact governed b-y traffic conditions in advance of said section and said iirst cam operated contact for said relay, and a stick circuit having two parallel paths one of which includes said tra'ic governed contact and the other of which includes said second and third cam operated contacts for said relay whereby said relay is picked up and released to effect the transfer from the supply of current impulses of positive polarity to the supply of current impulses of negative polarity or vice versa in one-half said operating v cycle.

6. In combination, a stretch of railway track l formed with an insulated track section, a source of direct current, an oscillating code transmitter having an oscillation cycle of a preselected interval and provided with a rst and a second coding contact closed as the code transmitter swings to a right-hand and a left-hand position respectively, a rst and a second auxiliary Contact means mounted on said code transmitter to close said rst auxiliary contact means at said right-hand position only and to open said second auxiliary contact means only during the swing from the left-hand to the right-hand position, a traflic controlled relay, a iirst circuit means including a back contact of said relay and said rst coding contact to couple said current source to the rails of said section for supplying code impulses of current of negative polarity to the rails, a second circuit means including a front contact of said relay and said second coding contact to couple said current source to the rails of said section for supplying code impulses of current of positive polarity to the rails, a traic controlled contact governed by a rst and a second traffic condition in advance of said section, `a pick-up circuit including said traiic controlled contact and said rst auxiliary contact means in series to energize said relay, and a stick circuit including said trafc controlled contact and said second auxiliary contact means in multiple to energize said relay.

WILLARD P. PLACE?. 

